The present invention relates to a technique for inhibiting and permitting a reshift if a reshift request is produced during another shift operation in an automatic transmission.
A reshift operation responsive to a reshift request produced during a first shift operation tends to cause shift shock or prolong the process of shift operation.
Published Japanese Patent Application Kokai Publication 8-338516; Published Japanese Patent Application Kokai Publication 8-277925; and Published Japanese Patent Application Kokai Publication 2-46352 show various reshift control systems.
It is an object of the present invention to provide a reshift control apparatus and/or process capable of reducing shift shock and improving shift response.
According to the present invention, a reshift control apparatus for an automatic transmission comprising a friction element group of friction engaging elements to be selectively engaged and disengaged to select one of gear ratios, comprises a shift controller configured: to govern a first shift operation to achieve a first shift to an after-first-shift gear ratio by setting a first shift target engagement pressure to engage a first shift engagement side element which is one element of the friction element group to be engaged for the first shift, and a second shift operation to achieve a second shift to an after-second-shift gear ratio different from the after-first-shift gear ratio by setting a second shift target engagement pressure to engage a second shift engagement side element which is one element of the friction element group to be engaged for the second shift and a second shift target disengagement pressure to disengage a second shift disengagement side element which is one element of the friction element group to be disengaged for the second shift; to allow a reshift to initiate the second shift operation during the first shift operation initiated in response to a first shift command when a reshift request for the second shift is produced in a first stage of the first shift operation; to make an actual fluid pressure for the second shift engagement side element after the time of the reshift command, equal to the second shift target engagement pressure varied with time from an intermediate state reached if the second shift operation were initiated at the time of the first shift command in the case of the second shift engagement side element being the same as the first shift engagement side element; and to make an actual fluid pressure for the second shift disengagement side element after the time of the reshift command, equal to the second shift target disengagement pressure varied with time from an intermediate state reached if the second shift operation were initiated at the time of the first shift command.
According to the present invention, a reshift control system for a vehicle, comprises: an automatic transmission comprising a gear train and a friction element group to determine a torque path in the gear train, to select one of gear ratios; a condition sensor to sense an operating condition of the vehicle; and a shift controller to govern a first shift operation in the automatic transmission from a before-shift gear ratio to an after-first-shift gear ratio, and a second shift operation in the automatic transmission from the before-shift gear ratio to an after-second-shift gear ratio, to produce a reshift command to command the second shift operation during the first shift operation in accordance with the operating condition; and to perform a reshift operation in response to the reshift command by terminating the first shift operation at an intermediate state without completing the first shift operation, and instead initiating the second shift operation from an intermediate state.
A reshift control process according to the present invention, for a vehicle equipped with an automatic transmission comprising a gear train and a friction element group to determine a torque path in the gear train, to select one of gear ratios, the reshift control process comprising: a step of producing a reshift command to command a second shift operation in the automatic transmission from a before-shift gear ratio to an after-second-shift gear ratio during a first shift operation in the automatic transmission from the before-shift gear ratio to an after-first-shift gear ratio in accordance with an operating condition of the vehicle; and a step of performing a reshift operation in response to the reshift command by terminating the first shift operation at an intermediate state without completing the first shift operation, and instead initiating the second shift operation from an intermediate state.
A reshift control apparatus according another aspect of the invention, comprises a shift controller configured: to produce a reshift request for a reshift to initiate a second shift operation during a first shift operation; and to inhibit the reshift after an end of a loss stroke in a friction engagement element to be engaged in the first shift operation is detected.
A reshift control apparatus according to still another aspect of the invention, comprises a shift controller configured: to produce a reshift request for a reshift to initiate a second shift operation during a first shift operation; to delay a reshift operation if the reshift request is produced in a reshift inhibit stage of the first shift operation, until an elapse of a delay time from an end of the first shift operation; and to decrease the delay time with increase in a measured time from the instant of the reshift request to the instant of an inertia phase end at which an effective gear ratio expressed as a transmission input and output speed ratio reaches a level of the after-first-shift gear ratio.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.